surface articulates with the hamate by a smooth, concave, oblong facet, which occupies its posterior and superior parts; it is rough in front, for the attachment of an interosseous ligament.

Articulations.The capitate articulates with seven bones: the navicular and lunate proximally, the second, third, and fourth metacarpals distally, the lesser multangular on the radial side, and the hamate on the ulnar side.

The Hamate Bone (os hamatum; unciform bone) (Fig. 228).The hamate bone may be readily distinguished by its wedge-shaped form, and the hook-like process which projects from its volar surface. It is situated at the medial and lower angle of the carpus, with its base downward, resting on the fourth and fifth metacarpal bones, and its apex directed upward and lateralward. The superior surface, the apex of the wedge, is narrow, convex, smooth, and articulates with the lunate. The inferior surface articulates with the fourth and fifth metacarpal bones, by concave facets which are separated by a ridge. The dorsal surface is triangular and rough for ligamentous attachment. The volar surface presents, at its lower and ulnar side, a curved, hook-like process, the hamulus, directed forward and lateralward. This process gives attachment, by its apex, to the transverse carpal ligament and the Flexor carpi ulnaris; by its medial surface to the Flexor brevis and Opponens digiti quinti; its lateral side is grooved for the passage of the Flexor tendons into the palm of the hand. It is one of the four eminences on the front of the carpus to which the transverse carpal ligament of the wrist is attached; the others being the pisiform medially, the oblique ridge of the greater multangular and the tubercle of the navicular laterally. The medial surface articulates with the triangular bone by an oblong facet, cut obliquely from above, downward and medialward. The lateral surface articulates with the capitate by its upper and posterior part, the remaining portion being rough, for the attachment of ligaments.

Articulations.The hamate articulates with five bones: the lunate proximally, the fourth and fifth metacarpals distally, the triangular medially, the capitate laterally.

6b. 2. The Metacarpus

The metacarpus consists of five cylindrical bones which are numbered from the lateral side (ossa metacarpalia I-V); each consists of a body and two extremities.

Common Characteristics of the Metacarpal Bones.The Body (corpus; shaft).The body is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front. It presents three surfaces: medial, lateral, and dorsal. The medial and lateral surfaces are concave, for the attachment of the Interossei, and separated from one another by a prominent anterior ridge. The dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in the fresh state, by the tendons of the Extensor muscles. This surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity. This ridge separates two sloping surfaces for the attachment of the Interossei dorsales. To the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.

The Base or Carpal Extremity (basis) is of a cuboidal form, and broader behind than in front: it articulates with the carpus, and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.

The Head or Digital Extremity (capitulum) presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx. It is broader, and extends farther upward,